Geological Survey Professional Paper 387—B Recent Activity of Glaciers of Mount Rainier, Washington

The advancing front of Carbon Glacier (map and figs. 1 and 4 on pl. 5) is closer to moraines which mark its maximum advance since postglacial times than any other major glacier at Mount Rainier. In September 1966, the front was barely more than half a mile upvalley from a moraine formed about A.D. 1760. Unlike some other glaciers at Mount Rainier which are advancing over stagnant ice, Carbon Glacier advanced about 250 feet over bedrock and gravel between July 1960 and September 1966 (time derived by comparison of aerial photographs).

Wonderland Trail passes within a few feet of the remnant of the terminal moraine from which ice started to recede about A.D. 1760 (table 6) (area 4) (fig. 5 on pl. 5). Two lateral moraines formed by minor readvances after the recession from the terminal moraine are prominent within the forest on the east side of Wonderland Trail (areas 1 and 2) opposite the point where the trail formerly crossed Carbon River. The older of these two, dating from 1835, is represented on the west side of Carbon River by a small ridge several hundred feet above the river (area 10), and at a lower altitude where it is crossed by the old trail (area 11).

TABLE 6.—Carbon Glacier: ages of trees sampled from periglacial features

[Periglacial features.: OW, outwash; M, moraine; FP, flood plain]

Sample area

The oldest moraines near the terminal moraine are short segments lying on each side of the valley. On the east side, the moraine (area 3) is 100 to 200 feet upslope from the younger moraines (areas 1 and 2). On the west side of the valley a small ridge (area 8) is seen where the Spray Park Trail turns up Cataract Creek a few feet south of the bridge (figs. 2 and 3 on pl. 5). A thick layer of yellowish-brown sandy volcanic ash which erupted from Mount St. Helens between 3,000 and 3,500 years ago (Crandell and others, 1962, p. D67) is present beneath till of the moraine and just beneath the forest humus less than 500 feet north of Cataract Creek. Thus Carbon Glacier has not advanced beyond this part of the valley in several thousand years.

Steep walls enclosing the narrow Carbon River valley combine with the steeply sloping valley floor to provide forces that have destroyed most moraines that once may have existed, especially on the east side of the valley. Gravity acting upon newly deposited moraines, aided by rock and snow avalanches from above, could have destroyed moraines that may have existed in many places on both sides of the valley.

The steeply sloping valley floor results in extreme velocities of water draining from the glacier. Floods of great size have destroyed parts of the terminal and lateral moraines and have left deposits of boulders like those in the Carbon River valley opposite the mouth of Cataract Creek. The Wonderland Trail crosses one of the flood channels supporting alder shrubs and small trees for some distance north (downvalley) of the 1760 moraine and south to the junction with the old trail near area 1a. Areas 12 and 13 are in this channel, as is area 14 west of Carbon River. The fact that the oldest trees in these areas started to grow between 1901 and 1907 suggests that a catastrophic flood occurred in Carbon River at the turn of the century which denuded most if not all of the flood-plain area. This flood probably was much larger than the November 23, 1959 flood that destroyed part of the Carbon River road up valley from Ipsut Creek campground.